Optical super lens suitable for extreme environment and preparation method thereof

Abstract

The invention relates to an optical super lens suitable for an extreme environment and a preparation method thereof, and the optical super lens comprises a super lens structure layer located at the center, and moth-eye membrane structure layers, an optical substrate and an optical composite membrane which are symmetrically disposed at two sides of the super lens structure layer. The super-lens structure layer, the moth-eye membrane structure layer and the optical substrate are respectively and independently made of wide-band-gap semi-conductive materials with the thermal conductivity of 50 W / m.K or above, and at least one structure parameter of the moth-eye membrane structure layer in the thickness direction of the optical substrate is modulated so as to complete refractive index transition from the super-lens structure layer to the optical substrate. According to the invention, the problem of efficiency reduction caused by refractive index mismatch is solved, and the optical super lens can work normally under extreme conditions such as high temperature or high power.

Description

Technical Field

[0001] The present invention relates to the technical field of optical elements, and in particular to an optical metalens suitable for extreme environments and a preparation method thereof. Background Art

[0002] Optical metalenses are lenses used to focus the entire visible light spectrum. By precisely controlling the phase of light, they can focus or defocus light in very thin structures, and even achieve a negative refractive index effect in some specific cases. The design of optical metalenses needs to take into account the phase changes of light waves, and this change often depends on the microstructure of the optical material. Traditional lens design is based on large-scale optical elements, while optical metalenses require fine structures at the micron or even nanometer level, which poses huge challenges in computing and manufacturing. For example, in the field of optical metalenses, to meet the needs of phase control, the structure in the optical metalenses needs to have a high refractive index, such as TiO2 or Si3N4. These materials are often amorphous or polycrystalline thin film materials. Due to their high cost and high mechanical brittleness, they cannot be directly made into independent self-supporting wafers. Therefore, the material structure commonly used in optical metalenses is to grow a high refractive index dielectric film on quartz glass to achieve phase control.

[0003] Due to its low thermal conductivity and laser damage threshold, quartz glass often faces the problem of optical metalens failure in high-temperature or high-power laser applications. This problem is mainly caused by the high-refractive-index optical metalens structure, which has a refractive index mismatch between its upper and lower interfaces, the quartz glass substrate, and the air interface. Once this refractive index mismatch occurs, Fresnel reflection will occur at the interface, which significantly reduces the transmittance of the optical metalens, resulting in a decrease in the efficiency of the optical metalens. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the first object of the present invention is to provide an optical metalens suitable for extreme environments, which solves the problem of reduced efficiency due to refractive index mismatch and enables the optical metalens to work normally under extreme conditions such as high temperature or high power.

[0005] A second object of the present invention is to provide a method for preparing an optical metalens suitable for extreme environments, which has the advantages of simple preparation, low cost and high yield.

[0006] To achieve the above first object, the present invention provides the following technical solutions: An optical metalens suitable for extreme environments includes a metalens structure layer located at the center, and a moth-eye film structure layer, an optical substrate, and an optical composite film symmetrically arranged on both sides of the metalens structure layer. The metalens structure layer, the moth-eye film structure layer, and the optical substrate are each independently composed of a wide-bandgap semiconductor material with a thermal conductivity of 50 W / m·K or higher. At least one structural parameter of the moth-eye film structure layer along the thickness direction of the optical substrate is modulated to complete the refractive index transition from the metalens structure layer to the optical substrate.

[0007] Furthermore, the super lens structure layer includes a plurality of nanorods arranged in a one-dimensional or two-dimensional array; and / or, the nanorods are mirror-symmetrical on a central plane parallel to the length direction of the optical substrate; And / or, the heights and periods of the plurality of nanorods are the same, the duty cycle increases along at least two array directions, and the at least two array directions (+X, -X, +Y, -Y) are opposite, intersecting and / or perpendicular array directions.

[0008] Furthermore, the wide bandgap semiconductor material of the nanorod is one or a combination of diamond, silicon carbide and gallium nitride with a bandgap width exceeding 2eV; and / or, the cross section of the nanopillar is circular, elliptical or polygonal; and / or, the height of the nanopillars is 200-1500 nm; and / or, the period of the nanorods is 250-900 nm; And / or, the duty cycle of the nanorods ranges from 20% to 90%.

[0009] Furthermore, the moth-eye film structure layer is composed of a plurality of frustum columns arranged in a two-dimensional array; And / or, the frustum is mirror-symmetrical on a central plane parallel to the thickness direction of the optical substrate; And / or, the heights and periods of the plurality of frustum columns are the same, and the diameters increase gradually from the nanocolumns to the optical substrate.

[0010] Furthermore, the wide bandgap semiconductor material of the truncated cone pillar is one or a combination of diamond, silicon carbide and gallium nitride with a bandgap width exceeding 2eV; And / or, the height of the frustum is 100-800 nm; And / or, the period of the frustum is 100-600 nm; And / or, the diameter of the frustum is in the range of 30 to 550 nm.

[0011] Furthermore, the optical substrate and the moth-eye film structure layer are integrally formed; And / or, the wide bandgap semiconductor material of the optical substrate is one or a combination of diamond, silicon carbide and gallium nitride with a bandgap width exceeding 2 eV; And / or, the thickness of the optical substrate is 100-5000 μm.

[0012] Furthermore, the optical composite film is formed by alternatingly stacking a plurality of low-refractive-index film layers having a refractive index not exceeding 1.7 and a high-refractive-index film layer having a refractive index exceeding 2.1; And / or, the low refractive index film layer is a composite film of one or more of silicon oxide and aluminum oxide; And / or, the high refractive index film layer is a composite film of one or more of titanium oxide and hafnium oxide; And / or, the optical composite film has a thickness of 0.5-50.0 μm.

[0013] To achieve the above second purpose, the present invention provides the following technical solutions: A method for preparing an optical metalens suitable for extreme environments comprises the following steps: S1: performing patterning on one side of the optical substrate to obtain a moth-eye film structure layer; S2 directly bonds a wide bandgap semiconductor material onto the moth-eye film structure layer obtained in S1, thins it to a predetermined height of the super lens structure layer, and then performs patterning to obtain a super lens structure layer; S3 directly bonds the super lens structure layer obtained in S2 to the moth eye film structure layer obtained in S1; S4 performs thin film deposition on the other side surface of the pair of optical substrates obtained in S3 to obtain an optical composite film.

[0014] Furthermore, in the S1, an equivalent refractive index distribution curve of the optical superlens structure formed by multiple nanocolumns is obtained in advance, and the refractive index variation range from the optical superlens structure to the optical substrate in the optical superlens plane is determined, and then the structural parameters of the moth-eye film structure are determined through the transition from the equivalent refractive index of the optical superlens to the refractive index of the optical substrate.

[0015] Furthermore, in the S1, exposure and development are first performed on one side surface of the optical substrate, and then a chrome mask is evaporated, and the chrome mask in the non-patterned area is peeled off, and then the optical substrate in the non-patterned area is etched to obtain a moth-eye film structure layer; wherein, the exposure dose and the development time are controlled to obtain a complete patterned area, and the thickness of the chrome mask evaporation is controlled so that it can be successfully peeled off.

[0016] Furthermore, in S2, the bonding pressure and temperature are controlled to ensure that the thermal expansion coefficients are not mismatched, the amount of thinning removal is controlled to ensure the thickness uniformity within the surface, and the patterning steps include coating, exposure, development, and pattern transfer.

[0017] Furthermore, in S3, the bonding pressure is controlled to ensure sufficient bonding strength and structural integrity.

[0018] Furthermore, in S4, the deposition time of each material of the thin film deposition is controlled to ensure the accuracy of the thickness.

[0019] In summary, the beneficial technical effects of the present invention are: 1. The present invention proposes to grow a moth-eye film structure on a substrate of a wide-bandgap semiconductor such as silicon carbide or diamond, prepare a thin layer of wide-bandgap semiconductor material on top, process an optical super-lens structure on the thin layer, and then bond it to a substrate that also has a moth-eye film structure to achieve a sandwich structure. The so-called moth-eye film structure imitates the special microstructure of the moth-eye surface. According to the equivalent medium theory, the refractive index of this structure is equivalent to that of a gradient multilayer film, and avoids the difficulties in preparing multilayer films and the low durability of the film. Therefore, it can be used as a refractive index transition layer between the substrate and the optical super-lens structure, and the same applies to the optical super-lens structure and the air. The present invention effectively solves the problem of reduced efficiency caused by refractive index mismatch in traditional optical super-lenses, and at the same time replaces the substrate material of the optical super-lens, so that the optical super-lens can work normally under extreme conditions such as high temperature or high power; 2. In order to achieve 2π phase control, the material of the nanopillars in the optical metalens of the present invention often has a very high refractive index, which leads to strong interface reflection between them and the air and the substrate, resulting in a reduction in propagation efficiency. On the basis of not changing the phase distribution design of the optical metalens, the present invention superimposes a layer of microstructure on the top and bottom to increase the transmittance of the interface between the nanopillars of the optical metalens and the air and substrate, thereby further improving the efficiency of the optical metalens. At the same time, the substrate and the optical metalens nanopillars are made of wide bandgap semiconductor materials (silicon carbide, diamond, etc.), which makes the optical metalens have stronger thermal stability and high power resistance. For optical metalens, this method can significantly improve the propagation efficiency without affecting the design of the optical metalens itself, thereby improving the utilization rate and strong stability of light energy in practical applications; 3. The present invention can effectively improve the low efficiency of traditional optical metalens due to refractive index mismatch. Using the method of this patent, the stability of high-efficiency optical metalens in extreme environments can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 2 is a schematic structural diagram of the optical metalens according to embodiment 1 of the present invention.

[0021] Figure 2 This is a flowchart of the method provided in Example 6 of the present invention.

[0022] Figure 3This is an equivalent refractive index distribution curve diagram of Example 7 of the present invention.

[0023] Figure 4 This is a transmittance curve diagram of Example 9 of the present invention.

[0024] In the figure, 1. Super lens structure layer; 11. Nano pillars; 2. Moth-eye film structure layer; 21. Frustum pillars; 3. Optical substrate; 4. Optical composite film. DETAILED DESCRIPTION

[0025] In order to make the technical means, creative features, objectives and functions achieved by the present invention clearer and easier to understand, the present invention is further explained below with reference to the accompanying drawings and specific implementation methods.

[0026] Example 1: Reference Figure 1 , an optical metalens suitable for extreme environments disclosed in the present invention, comprising a metalens structure layer 1 located at the center, and a moth-eye film structure layer 2, an optical substrate 3, and an optical composite film 4 symmetrically arranged on both sides of the metalens structure layer 1. The metalens structure layer 1, the moth-eye film structure layer 2, and the optical substrate 3 are each independently composed of a wide-bandgap semiconductor material with a thermal conductivity of 50 W / m·K or higher. At least one structural parameter of the moth-eye film structure layer 2 along the thickness direction of the optical substrate 3 is modulated to complete the refractive index transition from the metalens structure layer 1 to the optical substrate 3.

[0027] Example 2: This embodiment of the present invention discloses an optical metalens suitable for use in extreme environments. This embodiment differs from Example 1 in that, first, the metalens structure layer 1 comprises a plurality of nanopillars 11 arranged in a two-dimensional array along two mutually perpendicular directions (X and Y). The nanopillars 11 are mirror-symmetric about a central plane parallel to the length of the optical substrate 3. These nanopillars 11 have the same height and period, and the duty cycle increases along the two array directions (+X and -X). Specifically, the nanopillars 11 are made of a wide-bandgap semiconductor material, have a circular cross-section, a height of 1000 nm, a period of 400 nm, and a duty cycle ranging from 20% to 70%.

[0028] Secondly, the moth-eye film structure layer 2 consists of multiple truncated cones 21 arranged in a two-dimensional array along two mutually perpendicular directions (X and Y). The cones 21 are mirror-symmetric about a central plane parallel to the thickness of the optical substrate 3. These cones 21 have the same height and period, and their diameter increases from the nanomaterial pillars toward the optical substrate 3. Specifically, the cones 21 are made of diamond, have a height of 150 nm, a period of 250 nm, and a diameter ranging from 50 to 210 nm.

[0029] Again, the optical substrate 3 and the moth-eye film structure layer 2 are integrally formed. The optical substrate 3 is made of diamond and has a thickness of 400 μm.

[0030] Finally, the anti-reflection film is made up of several low-refractive index film layers (aluminum oxide film layers) and high-refractive index film layers (titanium oxide film layers) alternately stacked. The thickness of the anti-reflection film is 0.850μm. Starting from the air interface, the first layer is silicon oxide and the second layer is titanium oxide. They are stacked in sequence with thicknesses of 181.8nm, 125.7nm, 13.4nm, 90.9nm, 18.8nm, 102.7nm, 98.9nm, 84.6nm, 48.3nm, and 86.6nm, respectively, achieving high transmittance in the near-infrared band of 1000~1550nm.

[0031] Example 3: This is an optical metalens suitable for extreme environments disclosed in the present invention. It differs from Example 1 in that, first, the metalens structure layer 1 comprises a plurality of nanopillars 11 arranged in a two-dimensional array along two mutually perpendicular directions (X and Y). The nanopillars 11 are mirror-symmetric about a central plane parallel to the length of the optical substrate 3. These nanopillars 11 have the same height and period, and the duty cycle increases along the two array directions (+X and -X). Specifically, the nanopillars 11 are made of a wide-bandgap semiconductor material, have a circular cross-section, a height of 200 nm, a period of 250 nm, and a duty cycle ranging from 20% to 40%.

[0032] Secondly, the moth-eye film structure layer 2 consists of multiple truncated pyramidal pillars 21 arranged in a two-dimensional array along two mutually perpendicular directions (X and Y). The truncated pyramidal pillars 21 are mirror-symmetric about a central plane parallel to the thickness direction of the optical substrate 3. These truncated pyramidal pillars 21 have the same height and period, and their diameter increases from the nano-dielectric pillars toward the optical substrate 3. Specifically, the truncated pyramidal pillars 21 are made of diamond, silicon carbide, and gallium nitride, with a height of 800 nm, a period of 600 nm, and a diameter ranging from 450 to 550 nm.

[0033] Again, the optical substrate 3 and the moth-eye film structure layer 2 are integrally formed. The optical substrate 3 is made of diamond and has a thickness of 100 μm.

[0034] Finally, the antireflection film is made up of several low-refractive index film layers (silicon oxide film layers) and high-refractive index film layers (hafnium oxide layers) alternately stacked. The thickness of the antireflection film is 50.000μm, achieving high transmittance in the near-infrared band of 1000~1550nm.

[0035] Example 4: This embodiment of the present invention discloses an optical metalens suitable for use in extreme environments. This differs from Example 1 in that, first, the metalens structure layer 1 comprises a plurality of nanopillars 11 arranged in a two-dimensional array along two mutually perpendicular directions (X and Y). The nanopillars 11 are mirror-symmetric about a central plane parallel to the length of the optical substrate 3. These nanopillars 11 have the same height and period, and the duty cycle increases along the two array directions (+X and -X). Specifically, the nanopillars 11 are made of a wide-bandgap semiconductor material, silicon carbide, have a circular cross-section, a height of 1500 nm, a period of 900 nm, and a duty cycle ranging from 70% to 90%.

[0036] Secondly, the moth-eye film structure layer 2 consists of multiple truncated pyramidal pillars 21 arranged in a two-dimensional array along two mutually perpendicular directions (X and Y). The truncated pyramidal pillars 21 are mirror-symmetric about a central plane parallel to the thickness direction of the optical substrate 3. These truncated pyramidal pillars 21 have the same height and period, and their diameter increases from the nano-dielectric pillars toward the optical substrate 3. Specifically, the truncated pyramidal pillars 21 are made of gallium nitride, have a height of 100 nm, a period of 100 nm, and a diameter ranging from 30 to 100 nm.

[0037] Again, the optical substrate 3 and the moth-eye film structure layer 2 are integrally formed. The optical substrate 3 is made of silicon carbide and has a thickness of 5000 μm.

[0038] Finally, the antireflection film is made up of several low-refractive index film layers (silicon oxide and aluminum oxide film layers) and high-refractive index film layers (titanium oxide and hafnium oxide layers) alternately stacked. The thickness of the antireflection film is 0.500μm, achieving high transmittance in the near-infrared band of 1000~1550nm.

[0039] Example 5: This embodiment of the present invention discloses an optical metalens suitable for use in extreme environments. This differs from Example 1 in that, first, the metalens structure layer 1 comprises a plurality of nanopillars 11 arranged in a two-dimensional array along two mutually perpendicular directions (X and Y). The nanopillars 11 are mirror-symmetric about a central plane parallel to the length of the optical substrate 3. These nanopillars 11 have the same height and period, and the duty cycle increases along the two array directions (+X and -X). Specifically, the nanopillars 11 are made of wide-bandgap semiconductor material, gallium nitride, have a circular cross-section, a height of 600 nm, a period of 750 nm, and a duty cycle ranging from 40% to 60%.

[0040] Secondly, the moth-eye film structure layer 2 consists of multiple truncated pyramidal pillars 21 arranged in a two-dimensional array along two mutually perpendicular directions (X and Y). The truncated pyramidal pillars 21 are mirror-symmetric about a central plane parallel to the thickness direction of the optical substrate 3. These truncated pyramidal pillars 21 have the same height and period, and their diameter increases from the nano-dielectric pillars toward the optical substrate 3. Specifically, the truncated pyramidal pillars 21 are made of silicon carbide, have a height of 500 nm, a period of 300 nm, and a diameter ranging from 250 to 400 nm.

[0041] Again, the optical substrate 3 and the moth-eye film structure layer 2 are integrally formed. The optical substrate 3 is made of gallium nitride and has a thickness of 500 μm.

[0042] Finally, the antireflection film is made up of several low-refractive index film layers (silicon oxide and aluminum oxide film layers) and high-refractive index film layers (titanium oxide and hafnium oxide layers) alternately stacked. The thickness of the antireflection film is 0.800μm, achieving high transmittance in the near-infrared band of 1000~1550nm.

[0043] Example 6: Reference Figure 2 , which is a method for preparing an optical metalens suitable for extreme environments disclosed in the present invention, is different from Example 1 in that it includes the following steps: S1: performing patterning on one side of the optical substrate 3 to obtain a moth-eye film structure layer 2; S2 directly bonds a wide bandgap semiconductor material onto the moth-eye film structure layer 2 obtained in S1, thins it to a predetermined height of the superlens structure layer 1, and then performs patterning to obtain the superlens structure layer 1; S3: The super lens structure layer 1 obtained in S2 is directly bonded to the moth eye film structure layer 2 obtained in S1; S4 performs thin film deposition on the other side surface of the pair of optical substrates 3 obtained in S3 to obtain an optical composite film 4.

[0044] Example 7: A method for preparing an optical metalens with high focusing efficiency disclosed in the present invention, which is different from Example 6 in that it includes the following steps: S1 sets the deposition parameters of two film materials, silicon oxide and titanium oxide, in an electron beam evaporation coating device. At room temperature, the deposition rate of silicon oxide is 1.5 nm / s, and the deposition rate of titanium oxide is 3 nm / s. The deposition time of each layer is set, and several silicon oxide layers and titanium oxide layers are alternately deposited to obtain an antireflection film. In step S2, the other side of the optical substrate 3 is exposed and developed, followed by evaporation of a metal mask. The metal mask in the non-patterned area is then peeled off, and the non-patterned area of ​​the optical substrate 3 is etched to obtain a moth-eye film. The exposure dose is 20 nA, and the development time is 1 minute. This allows for a well-formed patterned area, and the thickness of the metal mask is kept below 80 nm to facilitate successful peeling. S3 first spin-coats photoresist (AZ1518) on the moth-eye film, removes the photoresist above the moth-eye film surface by dry etching, and then spin-coats photoresist (zep520) to a predetermined nano-dielectric column height. Then, the photoresist surface is exposed and developed, and a high-refractive index material is deposited in the patterned area. The high-refractive index material above the predetermined nano-dielectric column height is then removed by dry etching to obtain a plurality of nano-dielectric columns. The exposure dose is controlled to be 10 nA, the development time is 1 minute, the photoresist is spin-coated at a speed of 200 rps / min, and the photoresist is etched for 10 minutes. In addition, the deposition is performed at room temperature to ensure the integrity of the photoresist. S4 controls the bonding pressure to a moderate value to ensure the bonding strength without damaging the material structure; In step S5, the photoresist on the moth-eye film and the nano-dielectric pillars obtained in steps S3 and S4 is removed by wet stripping. The time for wet stripping using the acetone solution is controlled to be 1 hour, thereby obtaining the optical metalens shown in Example 2.

[0045] Example 8: A method for preparing an optical metalens with high focusing efficiency disclosed in the present invention is different from Example 7 in that, in S4, photoresist (AZ1518) is first spin-coated on the surface of the multiple nano-dielectric pillars and photoresist (zep520) obtained in S3 to a predetermined moth-eye film height, and then the photoresist surface is exposed and developed. After the material is deposited in the patterned area, the high-refractive index material above the predetermined thickness of the optical substrate 3 is removed by dry etching to obtain another moth-eye film and optical substrate 3, and then S1 is repeated; wherein, the exposure dose is controlled to be 10nA, the development time is 1min, the photoresist is spin-coated at a speed of 200rps / min, the photoresist is etched for 10min, and deposition is performed at room temperature to ensure the integrity of the photoresist; finally, the optical metalens shown in Example 3 is obtained.

[0046] Example 9: A method for preparing an optical metalens with high focusing efficiency disclosed in the present invention, which is different from Example 6 in that, in S2 and S4, referring to Figure 3 , pre-acquire the equivalent refractive index distribution curve of the optical metalens structure formed by multiple nano-dielectric columns, determine the refractive index variation range from the optical metalens structure to the optical substrate 3 in the optical metalens plane, and then determine the structural parameters of the moth-eye film through the transition from the equivalent refractive index of the optical metalens to the refractive index of the optical substrate 3, and finally obtain the enhanced transmittance. When the equivalent refractive index transition is not performed, the transmittance of the optical metalens is Figure 4 The curve where the hollow circle is located, after the calculation and design matching of the equivalent refractive index, the transmittance of the optical metalens is Figure 4From the curve where the solid circle is located, it can be seen that the transmittance of the optical metalens is effectively improved, thereby increasing the focusing efficiency.

[0047] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. An optical metalens suitable for extreme environments, characterized by: The invention comprises a super lens structure layer (1) located in the center, a moth-eye film structure layer (2) symmetrically arranged on both sides of the super lens structure layer (1), an optical substrate (3) and an optical composite film (4); the super lens structure layer (1), the moth-eye film structure layer (2) and the optical substrate (3) are each independently composed of a wide bandgap semiconductor material having a thermal conductivity of more than 50 W / m·K; at least one structural parameter of the moth-eye film structure layer (2) along the thickness direction of the optical substrate (3) is modulated to complete the refractive index transition from the super lens structure layer (1) to the optical substrate (3).

2. The optical metalens suitable for extreme environments according to claim 1, characterized in that: The super lens structure layer (1) includes a plurality of nanorods (11) arranged in a one-dimensional or two-dimensional array; and / or, the nanorods (11) are mirror-symmetrical on a central plane parallel to the length direction of the optical substrate (3); And / or, the height and period of the plurality of nanorods (11) are the same, and the duty cycle increases along at least two array directions, and the at least two array directions (+X, -X, +Y, -Y) are opposite, intersecting and / or perpendicular array directions.

3. The optical metalens suitable for extreme environments according to claim 3, characterized in that: The wide bandgap semiconductor material of the nanorod (11) is one or a combination of diamond, silicon carbide and gallium nitride with a bandgap width exceeding 2eV; and / or, the cross section of the nanorod (11) is circular, elliptical or polygonal; and / or, the height of the nanopillars (11) is 200-1500 nm; and / or, the period of the nanorods (11) is 250-900 nm; And / or, the duty cycle of the nanorods (11) ranges from 20% to 90%.

4. The optical metalens suitable for extreme environments according to claim 1, characterized in that: The moth-eye membrane structure layer (2) is composed of a plurality of frustum columns (21) arranged in a two-dimensional array; And / or, the frustum (21) is mirror-symmetrical on a central plane parallel to the thickness direction of the optical substrate (3); And / or, the heights and periods of the plurality of frustum columns (21) are the same, and the diameters increase gradually from the nanocolumns (11) to the optical substrate (3).

5. The optical metalens suitable for extreme environments according to claim 4, characterized in that: The wide bandgap semiconductor material of the truncated cone (21) is one or a combination of diamond, silicon carbide and gallium nitride with a bandgap width exceeding 2eV; and / or, the height of the frustum pillar (21) is 100-800 nm; And / or, the period of the truncated cone (21) is 100-600 nm; And / or, the diameter of the frustum (21) is in the range of 30 to 550 nm.

6. The optical metalens suitable for extreme environments according to claim 1, characterized in that: The optical substrate (3) and the moth-eye film structure layer (2) are integrally formed; And / or, the wide bandgap semiconductor material of the optical substrate (3) is one or a combination of diamond, silicon carbide and gallium nitride with a bandgap width exceeding 2eV; And / or, the thickness of the optical substrate (3) is 100-5000 μm.

7. The optical metalens suitable for extreme environments according to claim 1, characterized in that: The optical composite film (4) is formed by alternately stacking a plurality of low-refractive-index film layers with a refractive index not exceeding 1.7 and a high-refractive-index film layer with a refractive index exceeding 2.1; And / or, the low refractive index film layer is a composite film of one or more of silicon oxide and aluminum oxide; And / or, the high refractive index film layer is a composite film of one or more of titanium oxide and hafnium oxide; And / or, the thickness of the optical composite film (4) is 0.5-50.0 μm.

8. The method for preparing an optical metalens suitable for extreme environments according to any one of claims 1 to 7, characterized in that: The following steps are included: S1: performing patterning on one side of the optical substrate (3) to obtain a moth-eye film structure layer (2); S2 directly bonds a wide bandgap semiconductor material onto the moth-eye film structure layer (2) obtained in S1, thins the layer to a predetermined height of the super lens structure layer (1), and then performs patterning to obtain the super lens structure layer (1); S3 directly bonds the super lens structure layer (1) obtained in S2 to the moth eye film structure layer (2) obtained in S1; S4 performs thin film deposition on the other side surface of the pair of optical substrates (3) obtained in S3 to obtain an optical composite film (4).

9. The method for preparing an optical metalens suitable for extreme environments according to claim 8, wherein: In the S1, an equivalent refractive index distribution curve of an optical superlens structure formed by a plurality of nanopillars (11) is obtained in advance, and a refractive index variation range from the optical superlens structure to the optical substrate (3) within the optical superlens plane is determined. Then, the structural parameters of the moth-eye membrane structure are determined through the transition from the equivalent refractive index of the optical superlens to the refractive index of the optical substrate (3).

10. The method for preparing an optical metalens suitable for extreme environments according to claim 8, wherein: In the above-mentioned S1, exposure and development are first performed on one side surface of the optical substrate (3), and then a chrome mask is evaporated, and the chrome mask in the non-patterned area is peeled off, and then the optical substrate (3) in the non-patterned area is etched to obtain a moth-eye film structure layer (2).

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